RESEARCH PLAN: The P.I.s immediate career goal is to establish himself as an independent Principal Investigator at the University of California, Berkeley (UC-B). His long-term goal is obtaining a tenured faculty position in an environmental health sciences graduate program where he can conduct research in exposure/risk modeling and related occupational health topics, and contribute to formulating occupational health policy and research agendas. The proposed award would enable the investigator to acquire advanced skills in stochastic modeling and expertise in an appropriate programming language/system; knowledge gained by project work would be supplemented by taking several courses offered at UC-B. The investigator s mentor, Dr. Robert Spear, has extensive experience in stochastic modeling; the necessary office and computer resources are also available. The proposed research uses a modeling approach to investigate the risk of Mycobacterium tuberculosis (M. tb) infection among healthcare workers. The project has four specific aims. (1) A stochastic model will be developed that dynamically simulates a worker cohorts M. tb infection experience over a given time interval, e.g., five years. The model will incorporate variability in the tuberculosis (TB) patient count, in patient infectiousness, and in patient contact, and accommodate the potential that infected workers develop active TB and serve as new sources of infection. (2) The stochastic model would be used to investigate the impact of M. tb infection among immunocompromised healthcare workers, and thereby explore the need for on-the-job accommodation of employees at special risk. (3) A method for assessing dilution ventilation efficacy based on the local purging flowrate concept would be developed and used in a sample of TB patient isolation and treatment rooms. (4) The stochastic model and analytical model would be used to examine the cost-efficacy of alternative infection control measures. The analysis would account for differences in dilution ventilation efficacy close to and distant from the TB patient, as measured in the proposed field work.